1. Field of the Invention
The present invention relates to a tool position measurement method which is used for the precise measurement of the position of a tool that processes an object to be processed in a processing apparatus such as a semiconductor device assembly apparatus, etc., and the present invention further relates to an offset measurement method, a reference member and a bonding apparatus which are associated with the tool position measurement method.
2. Prior Art
In wire bonding apparatuses, for instance, the bonding head which is mounted on an XY table has a position detection camera and a bonding arm. The position detection camera images reference patterns on an object to be bonded such as semiconductor devices, etc., in order to specify the bonding points on the object to be bonded. The bonding arm is provided with a bonding tool (called xe2x80x9ctoolxe2x80x9d) at one end thereof so that the bonding tool performs bonding. The position detection camera and the bonding arm are installed on the bonding head with the optical axis of the position detection camera and the axial center of the tool separated from each other by a fixed distance. Thus, the tool and the bonding arm are prevented form interfering with the visual field of the position detection camera when the position detection camera images reference patterns on the object to be bonded. Generally, the distance between the optical axis of the position detection camera and the axial center of the tool is called an xe2x80x9coffsetxe2x80x9d.
The position detection camera determines a reference point for the purpose of ascertaining the position to which the tool is to be moved. Accordingly, it is extremely important to know exactly how far the position detection camera is offset from the tool. However, the actual offset amount between the position detection camera and the tool varies from instant to instant as a result of, for instance, deformation of the camera holder and bonding arm caused by radiant heat from the high-temperature bonding stage. Accordingly, it is necessary to correct the offset amount when bonding operations are initiated and with an appropriate timing during bonding operations.
A method for accomplishing the above purpose is shown in, for example, Japanese Patent Application Laid-Open (Kokai) No. S59-69939. In this method, a pressure mark is formed by a bonding tool in an appropriate location within the bonding range, the position of the bonding tool is detected by detecting the position of this pressure mark by a position detection camera, then the amount of offset is corrected based upon this position. Furthermore, in this method, the coordinates of the center of the pressure mark are determined by performing specified image processing on image data obtained by photoelectric conversion from the position detection camera, and the amount of offset is calculated based upon these coordinates.
However, in this conventional structure, the pressure marks of the tool are not always clear. Furthermore, unlike special patterns that are suitable for image processing, individual pressure marks show different shapes. Accordingly, the above-described detection method is not always accurate.
The present invention is to solve the above problems.
The object of the present invention is to provide a novel means that can accurately detect the position of a tool such as a bonding tool.
The above-object is accomplished by a tool position measurement method of the present invention in which:
a tool that performs a processing operation on an object to be processed is caused to approach a reference member disposed in a fixed position, the approach being made in a direction which crosses the direction of the processing operation of the tool, and
a positional relationship between the tool and the reference member is measured by detecting the contact between the tool and the reference member.
In the above method, the tool (a bonding tool, for instance) is caused to approach the reference member in a direction which crosses the direction of the processing operation that is done by the tool, and the positional relationship between the tool and the reference member is measured by detecting the contact between the tool and the reference member. In other words, the positional relationship between the tool and the reference member is measured by means of the contact that occurs between the tool and the reference member when the tool is caused to approach the reference member. Accordingly, the position of the tool can be determined more clearly and accurately than in a conventional method in which the measurement is done on a pressure mark. The reference member is provided exclusively for this purpose; and alternatively, a portion of the components of a bonding apparatus may be used as this reference member. It is also possible to use the object to be processed as a reference member.
The above object is further accomplished by unique steps of the present invention for an offset measurement method used in a processing apparatus that includes:
a position detection imaging device that images an object to be processed, and
a tool which is installed in an offset fashion with respect to the position detection imaging device and performs a processing operation on the object to be processed, and the unique steps of the present invention comprises:
a step in which the positional relationship between the position detection imaging device and the reference member disposed in a fixed position is measured by the position detection imaging device in a first attitude in which the position detection imaging device is caused to face the reference member,
a step in which the positional relationship between the tool and the reference member is measured by causing the tool to approach the reference member and detecting the contact between the tool and the reference member in a second attitude in which the tool is caused to face the reference member, and
a step in which the offset amount is determined based upon the measurement results and the amounts of movement of the position detection imaging device and the tool between the first attitude and second attitude.
In the above method, the positional relationship between the tool (bonding toll) and the reference member is measured by measuring the positional relationship between the position detection imaging device (camera, for instance) and the reference member by means of the position detection imaging device in the first attitude in which the position detection imaging device is caused to face the reference member, and then by causing the tool to approach the reference member and detecting the contact between the tool and the reference member in the second attitude in which the tool is caused to face the reference member. Then, the offset amounts are determined based upon these measurement results and the amounts of movement of the position detection imaging device and tool between the first and second attitudes. In this method, in regard to the order in which the measurement in the first attitude and the measurement in the second attitude are performed, either measurement can be performed first. The measurement of the positional relationship between the tool and the reference member in the first attitude is accomplished by causing the tool to approach the reference member and detecting the contact between the tool and the reference member. Accordingly, the position of the tool can be clearly and accurately determined.
In the above offset measurement method, in the second attitude, the tool and the reference member are caused to approach each other in a direction which crosses the direction of the processing operation of the tool.
Since the tool (bonding tool) and reference member are caused to approach each other in a direction which crosses the direction of the processing operation (bonding) of the tool in the second attitude. Accordingly, the position of the tool can be determined more clearly and accurately than in the conventional method that depends on the measurement of a pressure mark.
Furthermore, in the present invention, the detection of the contact between the tool and the reference member can be accomplished based upon variations in a vibration that is applied to the tool.
In this method, the detection of the contact between the bonding tool and the reference member is accomplished based upon the variations in a vibration that is applied to the tool. Accordingly, this method can be easily applied to an apparatus in which detection of the contact between a tool and an object to be processed is accomplished based upon the variations in a vibration that is applied to the tool.
Furthermore, the present invention provides a reference member which is held in a fixed position. This reference member is characterized in that the reference member comes into contact with the tool when a tool (bonding tool) which performs a processing operation (such as bonding) on an object to be processed is moved in a direction that crosses the direction of the processing operation. With the use of this reference member of the present invention, the position of the tool can be determined clearly and accurately.
The above reference member can be a hole that is formed in a clamping member that holds the object to be processed.
In the above, a hole formed in a clamping member which holds the object to be processed is used as a reference member. Thus, the reference member can be provided close to the object to be processed, and the amount of movement of the tool between processing operations and offset correction operations can be extremely small.
In the above reference member of the present invention, the rim or the edge that defines the hole have sides that run along directions of coordinate axes that are used in detecting the position of the tool.
In the above structure, the edge of the hole has sides that run along the directions of the coordinate axes used in the detection of the position of the tool. Accordingly, the processing that converts position information into position coordinates in the position detection operations is performed easily.
Furthermore, the above-described object is accomplished by a unique structure of the present invention for a bonding apparatus that comprises:
a position detection imaging device that images an object to be bonded, and
a tool which is installed so as to be offset with respect to the position detection imaging device and processes the object to be bonded, and
the bonding apparatus is provided with an operation control device which determines the offset amount between the position detection imaging device and the tool based upon:
a measured value that is obtained when the positional relationship between the position detection imaging device and a reference member disposed in a fixed position is measured by the position detection imaging device in a first attitude in which the position detection imaging device is caused to approach the reference member,
a measured value that is obtained when the positional relationship between the tool and the reference member is measured by detecting the contact between the tool and the reference member in a second attitude in which the tool is caused to approach the reference member, and
amounts of movement of the position detection imaging device and the tool between the first attitude and second attitude.
With this bonding apparatus, the position of the tool (bonding tool) can be determined more clearly and accurately than in a conventional method that uses a pressure mark, and the offset amount between the position detection imaging device and the tool is measured with accuracy.
The above object is further accomplished by another unique structure of the present invention for a bonding apparatus that comprises:
a position detection imaging device that images an object to be bonded,
a tool which is installed so as to be offset with respect to the position detection imaging device and which processes the object to be bonded,
an XY table which moves the position detection imaging device and the tool as an integral unit, and
a detection means which detects contact between the tool and the object to be bonded based upon variations in ultrasonic vibrations applied to the tool, and
the bonding apparatus is provided with an operation control device which determines an offset amount between the position detection imaging device and the tool based upon:
a measured value that is obtained when the positional relationship between the position detection imaging device and a reference member disposed in a fixed position is measured by the position detection imaging device in a first attitude in which the position detection imaging device is caused to approach the reference member by the XY table,
a measured value that is obtained when the positional relationship between the tool and the reference member is measured as a result of the contact between the tool and the reference member is detected by the detection means based upon variations in the ultrasonic vibrations applied to the tool in a second attitude in which the tool is caused to approach the reference member by the XY table, and
an amount of movement of the XY table between the first attitude and second attitude.
With the above bonding apparatus, the position of the tool (bonding tool) can be determined clearly and accurately, and the offset amount between the position detection imaging device and the tool is measure with accuracy.